Add async handler interfaces for connected and disconnected to allow async code to execute on connect

Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs

@@ -38,9 +38,9 @@ namespace MQTTnet.Extensions.ManagedClient
 
             _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
 
-            _mqttClient.Connected += OnConnected;
-            _mqttClient.Disconnected += OnDisconnected;
-            _mqttClient.ApplicationMessageReceived += OnApplicationMessageReceived;
+            _mqttClient.UseConnectedHandler(OnConnected);
+            _mqttClient.UseDisconnectedHandler(OnDisconnected);
+            _mqttClient.UseReceivedApplicationMessageHandler(OnApplicationMessageReceived);
 
             _logger = logger.CreateChildLogger(nameof(ManagedMqttClient));
         }
@@ -415,19 +415,22 @@ namespace MQTTnet.Extensions.ManagedClient
             }
         }
 
-        private void OnApplicationMessageReceived(object sender, MqttApplicationMessageReceivedEventArgs eventArgs)
+        private Task OnApplicationMessageReceived(MqttApplicationMessageHandlerContext context)
         {
-            ApplicationMessageReceived?.Invoke(this, eventArgs);
+            ApplicationMessageReceived?.Invoke(this, new MqttApplicationMessageReceivedEventArgs(context.SenderClientId, context.ApplicationMessage));
+            return Task.FromResult(0);
         }
 
-        private void OnDisconnected(object sender, MqttClientDisconnectedEventArgs eventArgs)
+        private Task OnDisconnected(MqttClientDisconnectedEventArgs eventArgs)
         {
             Disconnected?.Invoke(this, eventArgs);
+            return Task.FromResult(0);
         }
 
-        private void OnConnected(object sender, MqttClientConnectedEventArgs eventArgs)
+        private Task OnConnected(MqttClientConnectedEventArgs eventArgs)
         {
             Connected?.Invoke(this, eventArgs);
+            return Task.FromResult(0);
         }
 
         private void StartPublishing()

Source/MQTTnet/Client/Connecting/IMqttClientConnectedHandler.cs

@@ -0,0 +1,9 @@
+using System.Threading.Tasks;
+
+namespace MQTTnet.Client.Connecting
+{
+    public interface IMqttClientConnectedHandler
+    {
+        Task HandleConnectedAsync(MqttClientConnectedEventArgs eventArgs);
+    }
+}

Source/MQTTnet/Client/Connecting/MqttClientConnectedHandlerDelegate.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Client.Connecting
+{
+    public class MqttClientConnectedHandlerDelegate : IMqttClientConnectedHandler
+    {
+        private readonly Func<MqttClientConnectedEventArgs, Task> _handler;
+
+        public MqttClientConnectedHandlerDelegate(Action<MqttClientConnectedEventArgs> handler)
+        {
+            if (handler == null) throw new ArgumentNullException(nameof(handler));
+
+            _handler = context =>
+            {
+                handler(context);
+                return Task.FromResult(0);
+            };
+        }
+
+        public MqttClientConnectedHandlerDelegate(Func<MqttClientConnectedEventArgs, Task> handler)
+        {
+            _handler = handler ?? throw new ArgumentNullException(nameof(handler));
+        }
+
+        public Task HandleConnectedAsync(MqttClientConnectedEventArgs eventArgs)
+        {
+            return _handler(eventArgs);
+        }
+    }
+}

Source/MQTTnet/Client/Disconnecting/IMqttClientDisconnectedHandler.cs

@@ -0,0 +1,9 @@
+using System.Threading.Tasks;
+
+namespace MQTTnet.Client.Disconnecting
+{
+    public interface IMqttClientDisconnectedHandler
+    {
+        Task HandleDisconnectedAsync(MqttClientDisconnectedEventArgs eventArgs);
+    }
+}

Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedHandlerDelegate.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Client.Disconnecting
+{
+    public class MqttClientDisconnectedHandlerDelegate : IMqttClientDisconnectedHandler
+    {
+        private readonly Func<MqttClientDisconnectedEventArgs, Task> _handler;
+
+        public MqttClientDisconnectedHandlerDelegate(Action<MqttClientDisconnectedEventArgs> handler)
+        {
+            if (handler == null) throw new ArgumentNullException(nameof(handler));
+
+            _handler = context =>
+            {
+                handler(context);
+                return Task.FromResult(0);
+            };
+        }
+
+        public MqttClientDisconnectedHandlerDelegate(Func<MqttClientDisconnectedEventArgs, Task> handler)
+        {
+            _handler = handler ?? throw new ArgumentNullException(nameof(handler));
+        }
+
+        public Task HandleDisconnectedAsync(MqttClientDisconnectedEventArgs eventArgs)
+        {
+            return _handler(eventArgs);
+        }
+    }
+}

Source/MQTTnet/Client/IMqttClient.cs

@@ -14,7 +14,12 @@ namespace MQTTnet.Client
         bool IsConnected { get; }
         IMqttClientOptions Options { get; }
 
+        IMqttClientConnectedHandler ConnectedHandler { get; set; }
+        [Obsolete("Use ConnectedHandler instead.")]
         event EventHandler<MqttClientConnectedEventArgs> Connected;
+
+        IMqttClientDisconnectedHandler DisconnectedHandler { get; set; }
+        [Obsolete("Use DisconnectedHandler instead.")]
         event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
 
         Task<MqttClientAuthenticateResult> ConnectAsync(IMqttClientOptions options, CancellationToken cancellationToken);

Source/MQTTnet/Client/MqttClient.cs

@@ -44,8 +44,12 @@ namespace MQTTnet.Client
             _logger = logger.CreateChildLogger(nameof(MqttClient));
         }
 
+        public IMqttClientConnectedHandler ConnectedHandler { get; set; }
+
         public event EventHandler<MqttClientConnectedEventArgs> Connected;
 
+        public IMqttClientDisconnectedHandler DisconnectedHandler { get; set; }
+
         public event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
 
         public IMqttApplicationMessageHandler ReceivedApplicationMessageHandler { get; set; }
@@ -93,10 +97,12 @@ namespace MQTTnet.Client
                 }
 
                 IsConnected = true;
-                Connected?.Invoke(this, new MqttClientConnectedEventArgs(authenticateResult));
 
                 _logger.Info("Connected.");
 
+                Connected?.Invoke(this, new MqttClientConnectedEventArgs(authenticateResult));
+                await ConnectedHandler?.HandleConnectedAsync(new MqttClientConnectedEventArgs(authenticateResult));
+
                 return authenticateResult;
             }
             catch (Exception exception)
@@ -259,6 +265,7 @@ namespace MQTTnet.Client
 
                 _logger.Info("Disconnected.");
                 Disconnected?.Invoke(this, new MqttClientDisconnectedEventArgs(clientWasConnected, exception));
+                await DisconnectedHandler?.HandleDisconnectedAsync(new MqttClientDisconnectedEventArgs(clientWasConnected, exception));
             }
         }
 

Source/MQTTnet/Client/MqttClientExtensions.cs

@@ -15,6 +15,30 @@ namespace MQTTnet.Client
 {
     public static class MqttClientExtensions
     {
+        public static IMqttClient UseConnectedHandler(this IMqttClient client, Func<MqttClientConnectedEventArgs, Task> handler)
+        {
+            if (handler == null)
+            {
+                client.ConnectedHandler = null;
+                return client;
+            }
+
+            client.ConnectedHandler = new MqttClientConnectedHandlerDelegate(handler);
+            return client;
+        }
+
+        public static IMqttClient UseDisconnectedHandler(this IMqttClient client, Func<MqttClientDisconnectedEventArgs, Task> handler)
+        {
+            if (handler == null)
+            {
+                client.DisconnectedHandler = null;
+                return client;
+            }
+
+            client.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(handler);
+            return client;
+        }
+
         public static IMqttClient UseReceivedApplicationMessageHandler(this IMqttClient client, Func<MqttApplicationMessageHandlerContext, Task> handler)
         {
             if (handler == null)
@@ -143,7 +167,7 @@ namespace MQTTnet.Client
                 await client.PublishAsync(applicationMessage).ConfigureAwait(false);
             }
         }
-        
+
         public static Task<MqttClientPublishResult> PublishAsync(this IMqttClient client, string topic)
         {
             if (client == null) throw new ArgumentNullException(nameof(client));
@@ -175,7 +199,7 @@ namespace MQTTnet.Client
                 .WithPayload(payload)
                 .Build());
         }
-        
+
         public static Task<MqttClientPublishResult> PublishAsync(this IMqttClient client, string topic, string payload, MqttQualityOfServiceLevel qualityOfServiceLevel)
         {
             if (client == null) throw new ArgumentNullException(nameof(client));